This will send query to 192.168.11.2 at first. If 192.168.11.2 cannot resolve name, this will send query to 192.168.11.1. I do not know if this is a correct behavior.

3 Ubuntu 17.10's /etc/resolv.conf

Ubuntu 17.10's /etc/resolv.conf is the following. systemd-resolved responds when sending query to 127.0.0.53.

# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
# DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
# 127.0.0.53 is the systemd-resolved stub resolver.
# run "systemd-resolve --status" to see details about the actual nameservers.
nameserver 127.0.0.53

With enabling systemd debug log, switching from 192.168.11.2 to 192.168.11.1 is because systemd-resolved treats time of recursion query as timeout. I do not know why switching from
192.168.11.1 to 192.168.11.2.